by Renato Morano
I have a 1Hp 230VAC 60Hz National split type wall mount room air conditioner. It's been working well for quite few years now. Recently I experienced the system is having trouble. The compressor and fan(outdoor unit) is running while cooling the room for about 5 min. then shuts off. While the indoor unit keeps on running.
When the air gets warmer for about 2 min. the compressor & fan starts pumping cool air again. This happens continuously until I turn the unit off. I have checked the two Thermistors and found the coil sensor has reading on multi-amp tester only 2K Ohms. The air sensor has reading of 12K ohms. So I changed the coil sensor with a new one.
After this step I run the air con but the same problem still exist. The caps installed are 15uF on the compressor while 2uF on the fan respectively. I checked the caps of the compressor and fan respectively and shows on the multi-amp tester to be 14.43Uf and 1.9Uf respectively. So think both caps are still good.
However, I tried to run the system and took the voltage across the hot terminals of the two caps and got a reading of 342V. on compressor capacitor and 314V. on the fan cap.
This shows over-voltage and what's causing it is my next step to do. This most likely will involve the control card. May I have your analysis or comment on this problem please.